1. Field of the Invention
The present invention generally relates to a transmission gear apparatus for an automobile or a motor vehicle. More particularly, the present invention is concerned with a transmission gear apparatus for the motor vehicle which can ensure proper transmission gear ratios (also referred to as change gear ratio) for an engine starting operation effected by means of a dynamo-electric machine and an auxiliary machine driving operation performed by an internal combustion engine.
2. Description of Related Art
In a hitherto known or conventional transmission gear apparatus for the motor vehicle disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 264153/1990 (JP-A-2-264153), a pulley mounted on a rotatable shaft of the starter motor and a crank pulley connected to a crank shaft of an internal combustion engine (hereinafter also referred to simply as the engine) through the medium of a planetary gear mechanism are operatively coupled to each other by means of a transmission belt for transmitting a driving force or output torque to each other, and the transmission gear ratio is changed correspondingly in the engine starting operation mode and the electricity generating operation mode through cooperation of a one-way clutch provided between a carrier and a sun gear, ratchet mechanism for retaining/releasing an internal gear and an actuator for actuating the ratchet mechanism.
In the conventional transmission gear apparatus for the motor vehicle of the structure described above, a rotational motive power or output torque of a starter motor is transmitted to the crank pulley from the pulley of the starter motor through the transmission belt and then transmitted from the crank pulley to the crank shaft through the medium of a planetary gear mechanism with a rotation speed being reduced for thereby starting the operation of the engine.
In that case, a sun gear connected to the crank pulley rotates relative to a carrier coupled to the crank shaft at a higher velocity than the latter. However, after the engine starting operation has been completed, the internal gear retained by the ratchet mechanism is released while the starter motor is changed over to the electric generator. Consequently, the rotation speed of the sun gear connected to the crank pulley decreases while that of the carrier coupled to the crank shaft increases. At a time point at which the rotation speed (rpm) of the carrier increases just beyond that of the sun gear, the one-way clutch provided between the carrier and the sun gear is closed or clutched, as a result of which the carrier rotates in union with the sun gear.
When the carrier and the sun gear are operatively coupled to each other through the one-way clutch, an impact torque of large magnitude occurs due to significant difference in the rotation speed between the carrier and the sun gear, which brings about remarkably adverse influence to the life of the one-way clutch, giving rise to a problem.
Furthermore, in the conventional transmission gear apparatus, neither measures nor means is provided for absorbing or mitigating the impact which takes place when an excessively large torque is applied to the internal gear for same reason upon retaining the internal gear by the ratchet mechanism, providing another problem that the gears are injured.